The Effect of Substrate Roughness and Impact Angle on Droplet Spreading in Spraying

The effects of substrate roughness and impact angle on the spreading behavior of Polyvinylidene Fluoride (PVDF) slurry droplets during the spraying process using a dispersing disk are investigated, aiming to enhance the quality of lithium-ion battery separators. In this study, through theoretical modeling and simulation analysis, mathematical expressions for the maximum spreading coefficient and the final shrinking coefficient of the droplets are derived. A simulation model for droplet impact and diffusion on the substrate surface is established based on the Lattice Boltzmann Method (LBM) and the Lagrangian function. Simulation results indicate that the maximum spreading coefficient of the droplet decreases with increasing substrate roughness and impact angle, while the final shrinking coefficient increases with substrate roughness but decreases as the impact angle increases. Finally, spray coating experiments for lithium-ion battery separators are conducted, and the results show that as the surface roughness and impact angle of the substrate increase, the average diameter of the droplets decreases, thereby validating the accuracy of the simulation results.